It is known in the prior art to form a composite structure comprised of an initially open-cell resilient foam the open cells of which have been impregnated with an uncured thermosetting resin and at least one surface of which foam layer is overlaid with a layer of reinforcing material and wherein the foam layer is compressed to fill the open cells of the foam with the uncured resin and, further, wherein the excess resin is extruded outwardly to impregnate the reinforcing layer and which composite is cured while maintaining the foam in a compressed condition. The process results in a relatively impervious and rigidified composite structure. However, also in the past it has been the practice to prepare such preformed material as an individual, uncured, resin-impregnated sandwich immediately prior to the molding operation. Such individual or batch assembling of the preformed composite has the disadvantages of requiring a great deal of hand labor, thus increasing the cost of any product made in such fashion, and in making it difficult to accurately and consistently control the quantity of resin used and its dispersion throughout the composite.
The prior art teaches several methods for the preparation of such a composite preformed material and all of which methods are basically hand-layup or batch preparation methods. A first method taught by the prior art involves the placing of a first layer of reinforcing material, such as fiberglass mat, in a mold or on a platen; placing one or more layers of initially resilient and open-cell foam upon such reinforcing layer; pouring or otherwise spreading an uncured thermosetting resin over the surface of the resilient and open-cell foam; laying another sheet of reinforcing layer over the resin-coated surface of the foam; and thereafter compressing the reinforced foam layer with a movable mold member or platen to compress the composite to fill the open cells of the foam and extrude excess resin so as to impregnate the reinforcing layers and, while maintaining the composite in such a compressed condition, curing the thermosetting resin. Composite structures molded by the method described are generally shown in U.S. Pat. No. 3,193,437 Schafer, U.S. Pat. No. 3,867,221 Chant, and U.S. Pat. No. 3,944,704 Dirks.
Another method of preparing such composite includes the step of pre-impregnating the open-cell and resilient foam with an uncured thermosetting resin by passing the same through a reservoir of such resin and passing such foam material through rolls to extrude or wring out excess resin. Thereafter, the previous process is repeated wherein a first layer of reinforcing material is placed in a mold, followed by overlaying the resin-impregnated, resilient foam layer over the reinforcing layer, and finally completing the composite by overlaying the same with a second layer of reinforcing material after which the compressing and curing steps take place. Such pre-impregnated foam, utilizing dipping and wringing out liquid resin, is difficult to store in continuous lengths and usually results in the use of excess resin.